import java.awt.*;
import java.applet.*;

public class CrossLine extends Applet {
  DrawCrossLine drawing_CrossLine;
  Panel InputPanel;
  Panel LinePanel, PointPanel;

  TextField TFslope, TFintcpt, TFAx, TFAy;
  double slope=1.0, intcpt=-3.0, Ax=2.0, Ay=2.0;

  public void init() {
    setLayout(new BorderLayout());

    LinePanel = new Panel();
    LinePanel.add(new Label("Line l:  slope =", Label.RIGHT));
    LinePanel.add(TFslope  = new TextField(String.valueOf(slope),4));
    LinePanel.add(new Label("   intercept =", Label.RIGHT));
    LinePanel.add(TFintcpt = new TextField(String.valueOf(intcpt),4));

    PointPanel = new Panel();
    PointPanel.add(new Label("Point: A(x,y)=(", Label.RIGHT));
    PointPanel.add(TFAx = new TextField(String.valueOf(Ax),4));
    PointPanel.add(new Label(",", Label.CENTER));
    PointPanel.add(TFAy = new TextField(String.valueOf(Ay),4));
    PointPanel.add(new Label(")", Label.LEFT));

    InputPanel = new Panel();
    InputPanel.setLayout(new GridLayout(2,1));
    InputPanel.add(LinePanel);
    InputPanel.add(PointPanel);

    drawing_CrossLine = new DrawCrossLine(slope, intcpt, Ax, Ay);
    add("Center", drawing_CrossLine);
    add("South",  InputPanel);
  }

  public boolean action(Event ev, Object arg) {
    if (ev.target instanceof TextField) {
      slope  = Float.valueOf(TFslope.getText().trim()).floatValue();
      intcpt = Float.valueOf(TFintcpt.getText().trim()).floatValue();
      Ax     = Float.valueOf(TFAx.getText().trim()).floatValue();
      Ay     = Float.valueOf(TFAy.getText().trim()).floatValue();
      drawing_CrossLine.redraw(slope, intcpt, Ax, Ay);
      return true;
    } else if (ev.target instanceof Button) {
      return true;
    } else
      return true;
  }

  public boolean handleEvent(Event e) {
    if (e.id == Event.WINDOW_DESTROY) {
      stop();
      destroy();
      System.exit(0);
      return true;
    } else {
      return super.handleEvent(e);
    }
  }

  public static void main(String args[]) {
    PFrame f = new PFrame("A Line which crossing with right angle with line l");
    CrossLine CrossLine_function = new CrossLine();

    CrossLine_function.init();
    CrossLine_function.start();

    f.add("Center", CrossLine_function);
    f.resize(420, 500);
    f.show();
  }
}

class PFrame extends Frame {
  PFrame(String title) {
    super(title);
  }

  public boolean handleEvent(Event e) {
    if (e.id == Event.WINDOW_DESTROY) {
      dispose();
      System.exit(0);
    }
    return false;
  }
}
    
class DrawCrossLine extends Canvas {
  Font	font;
  double slope = 0.0, intcpt = -3.0, 
         Ax = -3.0, Ay = 2.0;
  Point A = new Point(0,0), B = new Point(0,0);
  Point O = new Point(0,0);
  Point U = new Point(20,20);
  int Height, Width;

  DrawCrossLine(double slope, double intcpt, double Ax, double Ay){
    this.slope = slope;
    this.intcpt = intcpt;
    this.Ax = Ax;
    this.Ay = Ay;
    repaint();
  }

  public void aw2px(Point t, int xx, int yy){
    t.x = (   xx * U.x) + O.x;
    t.y = ( - yy * U.y) + O.y;
  }

  public void aw2px(Point t, double x, double y){
    t.x = (int)(   x * (double)U.x + (double)O.x );
    t.y = (int)( - y * (double)U.y + (double)O.y );
  }

  public void draw_coordinate(Graphics g) {
    g.setColor(Color.pink);
    for (int i = -10; i <= 10; i++) {
      aw2px(A, -10,i);  aw2px(B,  10,i);
      g.drawLine(A.x, A.y, B.x, B.y);
    }
    for (int i = -10; i <= 10; i++) {
      aw2px(A, i,-10);  aw2px(B, i, 10);
      g.drawLine(A.x, A.y, B.x, B.y);
    }

    g.setColor(Color.black);
    g.setFont(font);
    aw2px(A,0,-10); aw2px(B,0, 10);
    g.drawLine(A.x, A.y, B.x, B.y);
    aw2px(A,-10,0); aw2px(B,10,0);
    g.drawLine(A.x, A.y, B.x, B.y);
  }

  public void paint(Graphics g) {
    Height = size().height;
    Width  = size().width;
    O.x = Height / 2;
    O.y = Width  / 2;

    draw_coordinate(g);

    g.setColor(Color.red);
    aw2px(A, -10.0, slope * -10.0 + intcpt);
    aw2px(B,  10.0, slope *  10.0 + intcpt);
    g.drawLine(A.x, A.y, B.x, B.y);

    aw2px(A, Ax, Ay);
    g.fillOval(A.x -5, A.y -5, 10, 10);

    double Sslope, Sintcpt;

    if ( slope != 0.0 ) {
      Sslope = -1.0 / slope;
    } else {
      g.drawString("Invalid!! Because of division by zero", 10, Height - 14);
      return;
    }
    Sintcpt = Ay - Sslope * Ax;

    aw2px(A, -10.0, Sslope * -10.0 + Sintcpt);
    aw2px(B,  10.0, Sslope *  10.0 + Sintcpt);
    g.drawLine(A.x, A.y, B.x, B.y);
    g.drawString("line: y = " + Sslope + "X + " + Sintcpt, 10, Height - 14);
  }

  public void redraw(double slope, double intcpt, double Ax, double Ay){ 
    this.slope = slope;
    this.intcpt = intcpt;
    this.Ax = Ax;
    this.Ay = Ay;
    repaint();
  }
}